TNF and obesity due to melanocortin 4 receptor deficiency: In addition, substantial evidence has indicated that excessive lipids stimulated the abnormalities of cytokines, including tumor necrosis factor-α (TNF-α) (6), interleukin-6 (IL-6), (7), and leptin (8), which gave rise to a vicious process that leads to fat deposition, and thus participates in the pathogenesis of obesity-associated MetS.